Field of the Invention
It has become accepted practice in the orthopedic field to use devices known as intramedullary nails to stabilize fractured bones. In particular, intramedullary nails are used for stabilizing fractures of the tibia and of the femur to thereby enable the bones to heal properly.
The nails are adapted for insertion into the intramedullary canal of the bone which may be reamed or left unreamed, depending on the situation at hand. Locking screws are often inserted through the bone to lock the nail in place. This method has proven valuable because it reduces the incidence and severity of malunion or displacement of the fracture. It allows the patient to apply weight to and walk on the injured bone earlier, thus, reducing the amount of muscle atrophy.
Various intramedullary nails have heretofore been known and disclosed int eh prior art. Prior art nails can be broken down by category:
First, many intramedullary nails have been proposed which are formed of a slid rod material. These have been found to be much too rigid to follow the usually imperfect intramedullary bone canal, and their insertion has all too often caused chipping of the bone material.
Nails formed of sheet metal have been proposed to provide greater flexibility. Some of these nails have been formed with closed cross-section and others have been formed into open cross-section configurations. To obtain desired flexibility/rigidity characteristics and to provide sufficient area about the nail to allow proper revascularization, such nails are generally formed with other than circular cross-section. This is, grooves on flat walls are often bent into the side walls of the sheet metal. Examples of such nails are found in U.S. Pat. No. 4,621,628 to Brudderman, U.S. Pat. No. 4,697,585 to Williams, European publication 0273872, U.S. publication 2,114,005, British publication 1,593,440, and Zimmer publication "A More Precise View of Interlocking Nails." Such sheet metal nails have proven to be relatively inefficient in their manufacture, and relatively difficult to modify in their configuration. More specifically, difficulties, inherent in the bending operation necessary to provide sheet metal nails with non-circular cross-section, have placed limitations on the ability to economically provide nails of cross-section which, for example, have grooves which are varied in their depth.
Other nails have been proposed which are formed from a rod material with a central longitudinal bore disposed therethrough. Such a bore provides a flexibility which is improved over that of the solid axis, but remains less than desirable. Examples of such nails are disclosed in U.S. Pat. No. 4,103,683 to Neufeld, U.S. Pat. No. 4,446,857 to Otte, et al., U.S. Pat. No. 4,622,959 to Marcus, European publication 0118778 and European publication 0008758.
Although the prior art nails have found varying degrees of success, there remains a need in the field for an intramedullary nail with a more desirable flexibility and with features which allow for easy and efficient modifications to the nail configuration during manufacture.